L ( θ ^ ν , θ ν ) = ∥ θ ^ ν − ⟨ θ ^ ν θ ν ⟩ θ ν ∥ 2 L(\widehat{\theta}_{\nu},\theta_{\nu})=\parallel\widehat{\theta}_{\nu}-\langle\widehat{\theta}_{\nu} \theta_{\nu}\rangle\theta_{\nu}\parallel^{2}